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субота, 30 листопада 2013 р.

Thorough testing can be harmful as we discovered recently. Extending our test coverage led us to a several-hours debugging session caused by just one line of code. What made the debugging particularly unpleasant was the fact that the code crashed not just the JVM it was deployed to, but also the virtual and/or physical machine underneath.

So, run the following at your own risk. Note that you have to provide the tools.jar in your classpath both for compilation and run-time.

The following are top 10 algorithms related concepts in coding interview. I will try to illustrate those concepts though some simple examples. As understanding those concepts requires much more efforts, this list only serves as an introduction. They are viewed from a Java perspective. The following concepts will be covered:

середа, 27 листопада 2013 р.

One of the best aspects of AWS-style cloud computing is the ability to quickly scale up in times of high traffic. Reddit, for example, temporarily added 40% extra capacity to cope with last year’s Obama AMA using Amazon’s cloud service.

However, while Bezo’s behemoth may be thebiggest cloud provider, it’s far from the only option available. Microsoft arestarting to take Azure seriously, and this week Google trumpeted the advantages of Google Compute Engine with an impressive demo of their load balancing service.

In the days before Nginx, the target was 10,000 simultaneous requests: now, Google haveshown off their virtualised infrastructure scaling up to 1,000,000 per second in just five seconds.

In May, Google Compute Engine hosted the backend for the Eurovision Song Contest companion app. The TV show is watched live by 125 million people across Europe, and its engineers managed to scale the app to a whopping 50,000 requests per second.

In comparison, wrote Voellm, the load generated in this experiment was 20 times that amount – equivalent to truly enormous massive spike in traffic. The million requests per second were served by 200 single-core VMs, each receiving approximately 5,000 requests per second.

The key boast for Google is the speed at which these VMs were spun up: apparently within five seconds and without any ‘pre-warming’ whatsoever. AWS’ Elastic Load Balancing service is nowhere near as flexible – requiring both a $49-monthly premium support agreement and notification of high traffic in advance.

Equally impressive is the fact that this setup cost just $10 USD. Granted, this might go up a notch when sending real responses (the service is billed by GB of data processed in addition to an hourly service charge), but still appears to be jaw-dropping value for money.

As AWS continues to dominate the market, it’s good to see real competition and innovation from rivals – even if it results in Google controlling even more of the internet.

It's Scala Day at Manning. Enhance your programming library with 50% off these selected Scala-related books. Just enter dotd1112tw in the Promotional Code box when you check out at manning.com to save half. Offer expires at midnight EST November 12, 2013.

середа, 6 листопада 2013 р.

R.I.P. GlassFish - Thanks for all the fish.

We've all heard it coming probably. Yesterday the official roadmap update for JavaEE and GlassFish wasupdated and published. And beginning with the title the whole post was basically about one thing: GlassFish Server as we know it today is deprecated from a full blown product to a toy product.

The Long Road from Sun to OracleGlassFish was something to worry about right from the start. After the merger it took some time to silence the voices which insisted on "Oracle killing GlassFish". Oracle did a decent job in nurturing the community and keeping their stuff together. I've written acouple of blogsmyself helping to get the word out. The 100-day releases 2.1.2 and 3.0.1 have somehow become the milestone to prove the will to improve. And we all have been fine with it after a while. Even back in January 2013 Icompiled a list of open source application serversand which one to pick. The final criteria was vendor support. That kicked WAS CE out of the game. As of yesterday it would also removed GlassFish. The two remaining alternatives burned down to one: Which is JBoss AS7 / WildFly.